阅读说明：本技术 一种取向碳纳米管-金属基复合材料导热盘的制备方法 (Preparation method of oriented carbon nanotube-metal matrix composite heat conducting disc ) 是由 任淑彬 黄建国 赵文茹 肖承龙 曲选辉 于 2021-08-25 设计创作，主要内容包括：一种碳纳米管-金属基复合材料导热盘的制备方法,属于粉末冶金领域。首先采用浆料法制备金属基/碳纳米管复合粉末,即将预先退火的金属粉末与经过超声破碎分散的碳纳米管一同放在去离子水中进行机械搅拌,搅拌直至透明状后,再将溶液过滤所得粉末进行烘干,得到碳纳米管均匀分散在金属粉体表面的复合粉；接着将复合粉末装入石墨模具中,采用热压的方式压制成取向碳纳米管-金属基复合材料。该方法具有界面可分离的显著优点,能够适用于目前各种模块化设备即插即用式的高效热输运工况,尤其利于在轨组装模块化航天器的发展；相比于基于垂直碳纳米管阵列的可分离式热界面材料,直接引入分散的碳纳米管不仅缩短了工艺流程,还极大地降低了制造成本。(A preparation method of a carbon nano tube-metal matrix composite heat conducting disc belongs to the field of powder metallurgy. Firstly, preparing metal-based/carbon nanotube composite powder by adopting a slurry method, namely placing pre-annealed metal powder and carbon nanotubes dispersed by ultrasonic crushing into deionized water to be mechanically stirred until the mixture is transparent, and then filtering the solution to obtain powder and drying the powder to obtain the composite powder in which the carbon nanotubes are uniformly dispersed on the surface of the metal powder; and then, filling the composite powder into a graphite mold, and pressing into the oriented carbon nanotube-metal matrix composite material by adopting a hot pressing mode. The method has the remarkable advantage of separable interface, can be suitable for the plug-and-play type high-efficiency heat transport working condition of various kinds of current modular equipment, and is particularly beneficial to the development of an on-orbit assembly modular spacecraft; compared with a separable thermal interface material based on a vertical carbon nanotube array, the direct introduction of the dispersed carbon nanotubes shortens the process flow and greatly reduces the manufacturing cost.)

1. A preparation method of an oriented carbon nanotube-metal matrix composite material heat conduction plate has ultralow interface thermal resistance orientation, and is characterized by comprising the following specific steps:

s1, preparing metal matrix/carbon nanotube composite powder by a slurry method, namely placing pre-annealed metal powder and the carbon nanotubes which are crushed and dispersed by ultrasound into deionized water to be mechanically stirred until the mixture is transparent, and then filtering the solution to obtain powder and drying the powder to obtain composite powder in which the carbon nanotubes are uniformly dispersed on the surface of the metal powder;

s2, filling the composite powder into a graphite mold, and pressing into the oriented carbon nanotube-metal matrix composite material in a hot pressing mode;

s3, sequentially performing mechanical polishing and electrolytic polishing to enable the nanotubes between the powder particles on the contact surface to be detected;

and S4, finally, the metal matrix composite material with the oriented carbon nanotubes on the contact surface is in close contact with a heat source under certain pressure, so that the oriented carbon nanotubes with ultrahigh thermal conductivity fill the gap between the two contact interfaces, thereby increasing a heat flow path and reducing the thermal contact resistance between the two interfaces.

2. The method for preparing an aligned carbon nanotube-metal matrix composite heat conducting plate according to claim 1, wherein the metal powder is copper powder, aluminum powder, titanium powder or their respective alloy powder, and the average grain size is 30-50 μm.

3. The method for preparing the oriented carbon nanotube-metal matrix composite heat conducting plate according to claim 1, wherein the metal powder is pre-annealed at a temperature of not higher than 200 ℃/h, the temperature is 50-70% of the melting point of the corresponding metal or alloy powder, the holding time is not less than 30min, the method is carried out under the protection of reducing atmosphere, inert gas or vacuum, and the heat conducting plate is cooled to room temperature by furnace cooling or air cooling after being held; the reducing atmosphere comprises hydrogen, decomposed ammonia, converted natural gas and coal gas.

4. The preparation method of the oriented carbon nanotube-metal matrix composite heat conducting disc as claimed in claim 1, wherein when the carbon nanotubes are dispersed by adopting an ultrasonic crushing mode, the ultrasonic frequency is not higher than 40kHz, the ultrasonic time is 10-30 min, the temperature is not higher than 80 ℃, the dispersing agent is an aqueous solution of a common anionic surfactant, and the concentration is not lower than 100 mg/L; the common anionic surfactants comprise carboxylate, sulfonate, sulfate ester salt and phosphate ester salt.

5. The method according to claim 1, wherein the material is prepared by hot pressing at a temperature rise rate of not higher than 20 ℃/min, at a holding/sintering temperature of 70-85% of the melting point of the corresponding metal or alloy powder, under a pressure of not lower than 20MPa, for a holding time of not lower than 2h, at a vacuum of not lower than 0.3Pa, and after the hot pressing, the sample is furnace-cooled to room temperature.

6. The method for preparing the oriented carbon nanotube-metal matrix composite heat conducting disc as claimed in claim 1, wherein the sample is washed with acetone and absolute ethanol before electropolishing, phosphoric acid is used as an electrolyte, the volume fraction of the electrolyte is 40-60%, the current is controlled to be about 0.3A during constant current electrolysis, and the electropolishing time is not less than 2 min.

7. The method of claim 6, wherein the length of the carbon nanotubes protruding from the contact interface can be controlled by controlling the electropolishing time to adapt to different conditions.

Technical Field

The invention belongs to the field of powder metallurgy, and particularly relates to a preparation method of an oriented carbon nanotube-metal matrix composite heat conducting disc.

Background

With the continuous deepening of the exploration pace of human space, the functional requirements on the spacecraft or space system are higher and higher, the volume and the weight of the corresponding spacecraft are increased continuously, and the large-scale spacecraft is difficult to be launched to the space at one time by depending on the existing launching technology. Modular on-track assembly is the best way to solve this problem recognized at home and abroad. The technology firstly designs the spacecraft or the space system in a modularized mode according to functions, then launches different functional modules into space step by step, and then mechanically connects the modules and a main module (such as a satellite) through an in-orbit assembly method according to specific functional requirements so as to meet specific functional requirements. A large part of the functional modules are high-power electrical appliance modules which generate a large amount of heat during working, and whether the heat can be effectively radiated is related to whether the functional modules can stably work. But due to structural limitations the module does not have its own cooling function. When the module is designed, the heat dissipation problem is solved by cooling the heat generated by the module through a cooling system carried by the main space station. It is therefore critical to ensure a smooth heat transfer path between the standard module and the main module with the two mating disks (heat transfer disks).

For solid-solid interface heat transfer between two heat conducting discs, only a few convex parts are in close contact to conduct heat transfer when actual rough solid surfaces are in contact, and most of the surrounding air is gap air to conduct heat transfer through radiation, so when heat is transferredWhen the flow passes through this interface, interface contact resistance is generated due to heat flow contraction. The presence of Thermal contact resistance severely limits the performance of high Thermal conductivity heat sinks, where Thermal Interface Materials (TIMs) should be generated. The TIMs are filled between the surfaces of two contacting solids, so that the actual contact area can be increased, the heat flow transport capacity is improved, and the ideal effect is that a material with high thermal conductivity is adopted to replace a space filled with air between the two solids and is tightly bonded with the matrix. The current commercial thermal interface materials comprise organic thermal interface materials (such as heat conducting paste and heat conducting gel, and the self thermal resistance of the materials is between 10 and 20mm²K/W), low melting point alloy solder (mainly composed of Sn, Ag, Cu, etc., and the material itself has heat resistance<5mm²K/W) and phase-change materials, but all of the materials have the problem of inseparable interface, and are not suitable for heat transfer of an on-orbit assembly modular spacecraft.

Researches show that the thermal conductivity of a single-walled carbon nanotube at room temperature is higher than 6000W/(m.K), the experimental thermal conductivity of a single multi-walled carbon nanotube at room temperature is also higher than 3000W/(m.K), the single-walled carbon nanotube has a low radial in-plane expansion coefficient and a shape adaptable to contact surface roughness, and the only defect is that the carbon nanotube is easy to agglomerate under the action of Van der Waals force. Therefore, how to uniformly disperse the carbon nanotubes on the surface of the metal powder, form a good composite relationship with the metal matrix and form an orientation at the contact interface, and fill the gap between the two contact interfaces to reduce the interface thermal resistance becomes a key for developing a heat conducting disc with ultra-low interface thermal resistance suitable for modular heat dissipation.

Disclosure of Invention

The invention aims to realize the preparation of a separable oriented carbon nanotube-metal matrix composite heat conducting disc with ultralow interface thermal resistance, so as to be suitable for plug and play type heat transport working conditions of various kinds of current modular equipment, and especially to ensure high-efficiency heat transport between on-orbit assembled modular spacecrafts.

The invention provides a preparation method of an oriented carbon nanotube-metal matrix composite heat conducting disc, which has ultralow interface thermal resistance and is characterized by comprising the following specific steps:

s1, preparing metal matrix/carbon nanotube composite powder by a slurry method, namely placing pre-annealed metal powder and the carbon nanotubes which are crushed and dispersed by ultrasound into deionized water to be mechanically stirred until the mixture is transparent, and then filtering the solution to obtain powder and drying the powder to obtain composite powder in which the carbon nanotubes are uniformly dispersed on the surface of the metal powder;

s2, filling the composite powder into a graphite mold, and pressing into the oriented carbon nanotube-metal matrix composite material in a hot pressing mode;

s3, sequentially performing mechanical polishing and electrolytic polishing to enable the nanotubes between the powder particles on the contact surface to be detected;

and S4, finally, the metal matrix composite material with the oriented carbon nanotubes on the contact surface is in close contact with a heat source under certain pressure, so that the oriented carbon nanotubes with ultrahigh thermal conductivity fill the gap between the two contact interfaces, thereby increasing a heat flow path and reducing the thermal contact resistance between the two interfaces.

Furthermore, the metal powder can be copper powder, aluminum powder, titanium powder or respective alloy powder, the average grain size is 30-50 μm, the temperature rise rate is required to be not higher than 200 ℃/h in the pre-annealing process, the heat preservation temperature is 50% -70% of the melting point of the corresponding metal or alloy powder, the heat preservation time is not lower than 30min, the metal powder can be carried out under the protection conditions of reducing atmosphere (hydrogen, decomposed ammonia, converted natural gas, coal gas and the like), inert gas or vacuum, and the metal powder is cooled to the room temperature by adopting a furnace cooling or air cooling mode after heat preservation.

Further, when the carbon nano tube is dispersed by adopting an ultrasonic crushing mode, the ultrasonic frequency is not higher than 40kHz, the ultrasonic time is 10-30 min, the temperature is not higher than 80 ℃, the dispersing agent is an aqueous solution of common anionic surfactants (carboxylate, sulfonate, sulfate ester salt and phosphate ester salt), and the concentration is not lower than 100 mg/L.

Further, when the material is prepared by adopting a hot pressing mode, the heating rate is not higher than 20 ℃/min, the heat preservation/sintering temperature is 70% -85% of the melting point of the corresponding metal or alloy powder, the applied pressure is not lower than 20MPa, the heat preservation and pressure maintaining time is not lower than 2h, the vacuum degree is not lower than 0.3Pa, and the sample is cooled to the room temperature along with the furnace after the hot pressing is finished.

Furthermore, the sample needs to be cleaned by acetone and absolute ethyl alcohol respectively before electrolytic polishing, phosphoric acid is used as electrolyte, the concentration of the electrolyte is between 40% and 60%, the current is controlled to be about 0.3A in the constant-current electrolytic process, and the electrolytic polishing time is not less than 2 min.

Further, the length of the carbon nano tube protruding from the contact interface can be controlled by controlling the time of the electrolytic polishing so as to adapt to different working conditions.

The main advantages of the invention are: (1) the carbon nano tube with excellent electric conduction and thermal conduction performance is used as a main strengthening phase, so that the performance of a metal matrix can be improved, and the oriented distribution can be formed on a contact interface, so that the oriented carbon nano tube with ultrahigh thermal conductivity can fill a gap between the two contact interfaces, a heat flow path is increased, and the thermal contact resistance between the two interfaces is greatly reduced; (2) compared with the traditional method of adding organic thermal interface materials such as heat conducting paste, heat conducting gel and the like and adopting low-melting-point alloy solder, phase change material and the like to reduce solid-solid interface thermal resistance, the method has the obvious advantage of separable interface, can be suitable for plug-and-play type high-efficiency heat transportation working conditions of various current modular equipment, and is particularly beneficial to the development of current on-orbit assembled modular spacecraft; (3) compared with the prior separable thermal interface material based on the vertical carbon nanotube array, the method has the advantages that the dispersed carbon nanotubes are directly introduced, and the oriented carbon nanotube-metal matrix composite material heat conducting disc is prepared by adopting a hot pressing method, so that the process flow is shortened, the manufacturing cost is greatly reduced, and the industrial production is facilitated.

Drawings

FIG. 1 is a process flow for preparing a heat conducting plate made of oriented carbon nanotube-metal matrix composite,

FIG. 2 shows the surface morphology of the nanotube-copper composite powder prepared by the slurry method,

FIG. 3 shows an aligned carbon nanotube-copper composite material prepared by a hot pressing method at 920 ℃ and 30MPa for 2h,

FIG. 4 shows the surface morphology of the aligned carbon nanotube-copper composite material after electropolishing,

FIG. 5 is a graph showing the change in interfacial thermal resistance with the same mating surface before and after electropolishing as a function of pressure.

Detailed Description

Example 1 preparation method of oriented carbon nanotube-copper-based composite material heat conduction plate with ultralow interface thermal resistance

Firstly, copper powder pretreatment: putting 18g of electrolytic copper powder with the average grain size of 38 mu m into a hydrogen atmosphere at 600 ℃ for heat preservation for 2h, and then air-cooling to room temperature;

secondly, weighing 0.027g of carbon nano tube, taking an aqueous solution of sodium hexadecylsulfonate as a dispersing agent, setting the concentration to be 1g/L, setting the ultrasonic frequency to be 30kHz, setting the temperature to be 60 ℃, continuously carrying out ultrasonic treatment for 20min, and then putting the carbon nano tube into a vacuum drying oven for drying;

thirdly, the mixed powder prepared by the slurry method is filled into a graphite die with the diameter of 20mm, the graphite die is heated to 920 ℃ according to the heating rate of 10 ℃/min, the pressure of 30MPa is slowly applied, the heat preservation is carried out for 2h under the pressure, and the vacuum degree reaches 3 multiplied by 10^-1Pa, after hot pressing, cooling to room temperature along with the furnace, and finally demoulding to obtain a Cu-0.15 wt% CNTs composite material heat conducting disc;

fourthly, mechanically polishing the sintered sample after being respectively ground by 600 meshes of sand paper, 800 meshes of sand paper, 1200 meshes of sand paper, 1500 meshes of sand paper, 2000 meshes of sand paper and 3000 meshes of sand paper, and performing electrolytic polishing when the surface scratches are few;

and fifthly, cleaning the mechanically polished sample by acetone and absolute ethyl alcohol respectively, putting the sample into phosphoric acid electrolyte with the volume fraction of 52%, and electrolyzing by adopting a constant current of 0.3A for 2min to obtain the copper-based composite material with the nanotube directionally distributed on the contact surface.

Embodiment 2, a method for preparing an oriented carbon nanotube-aluminum matrix composite heat conducting disk with ultra-low interface thermal resistance

Firstly, pretreating aluminum powder: putting 8g of aluminum powder with the average grain size of 42 mu m into 350 ℃ vacuum for heat preservation for 2h, and then cooling to room temperature along with a furnace;

secondly, weighing 0.016g of carbon nano tube, adopting an aqueous solution of ammonium dodecyl sulfate as a dispersing agent, setting the concentration to be 0.8g/L, setting the ultrasonic frequency to be 30kHz and the temperature to be 60 ℃, continuously carrying out ultrasonic treatment for 20min, and then putting the carbon nano tube into a vacuum drying oven for drying;

thirdly, the mixed powder prepared by the slurry method is filled into a graphite die with the diameter of 30mm, the graphite die is heated to 530 ℃ according to the heating rate of 10 ℃/min, the pressure of 25MPa is slowly applied, the heat preservation is carried out for 2h under the pressure, and the vacuum degree reaches 3 multiplied by 10^-1Pa, after hot pressing, cooling to room temperature along with the furnace, and finally demoulding to obtain the Al-0.2 wt% CNTs composite material heat conducting disc;

fourthly, the sintered sample is respectively ground by 600 meshes of sand paper, 800 meshes of sand paper, 1200 meshes of sand paper, 1500 meshes of sand paper and 2000 meshes of sand paper and then is mechanically polished, and when the surface scratches are few, electrolytic polishing is carried out;

and fifthly, cleaning the mechanically polished sample by acetone and absolute ethyl alcohol respectively, putting the sample into phosphoric acid electrolyte with the volume fraction of 48%, and electrolyzing by adopting a constant current of 0.3A for 2.5min to obtain the aluminum-based composite material with the nanotube oriented distribution on the contact surface.